The existence and biochemical mechanisms of organ-specific toxicity are the subject of heightened interest among toxicologists. Earlier studies in this laboratory described selective necrosis of pulmonary non-ciliated bronchiolar (Clara) cells following administration of naphthalene to mice. No damage to other lung cells was noted and no pathologic changes, as evidenced by histology or enzymic alterations, were observed. The work described in this section describes conditions under which 1,1-dichloroethylene (DCE) produces selective damage to mouse lung without morphologic or enzymatic evidence of nephro- or hepatotoxicity. Accompanying the lung damage there was a significant impairment of pulmonary cytochrome P-450 linked monooxygenase activities. Simultaneous with these changes there was a paradoxical increase in certain of these activities in kidney; these increases were found to be the result of enzyme induction.